How To Freeze Yeast (And Keep It For Years)

Freezing yeast allows you to store it for years, so you’ll always have the right yeast on hand for your next brew day. I’m going to show you the entire process to do it, and attempt to demonstrate that this really works by reviving a yeast I froze over three years ago.
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YEAST STARTER VIDEO: • Canning Wort For Yeast...
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[@RedHotBagel]

Ehm, no Martin. Once you break open the jar, you cannot keep it around. The whole idea behind pressure cooking is to kill off anything that might be in there, including spores. You are not working under a flow hood, so stuff falls in. Worse, you seem to use the yeast contaminated syringe to draw out the solution. Now you have another yeast strain in the medium. Not all vials come pre-sterilized, folks should make sure the ones they get are - or they need to change protocol! Prep the vials with the medium and pressure cook those. That's the better way to prep anyways, because now you are actually able to keep prepped vials around forever.

[@travisbeagle5691]

Just did a dry run of exactly that today using just water and 50 ml autoclavable vials. I filled them half way like I would with the glycerin mixture and was easily able to get them to seal properly. I'm going to prep a batch of vials tomorrow and put a few of them to use probably on Saturday. This is my process: fill the vial half way with the mixture; put the caps on just shy of finger tight; run a canning cycle like what's shown in the video; then tighten the lids once the pressure canner bleeds down to atmosphere.

[@pestalinc]

My thoughts exactly on what the Canning step was for. As an alternative you could use a Sous Vide machine to pasteurize. May work even better for doing the individual vials. But defiantly cant open the jar and reclose without re pasteurizing. Always fallow the three rules of brewing. Sanitation Sanitation and Sanitation.

[@andyh7537]

@@pestalinc - At best - you could do a tyndallization with the sous vide bath. The pressure cooker will do a full sterilization.

[@perfectworldpat7053]

Is the pressure cooker really necessary if it's not done to every piece of equipment? And for home brewers, and not yeast laboratories that need perfection, Aren't we getting these micro amounts of spores anyway? It seems to me that the pressure sterilization is only necessary if you need perfect reproductions many many many times.

[@tim-tim-timmy6571]

Very great video. Quite close to what we do in the lab. The isopropanol bath is a really great thing to do as it cools down homogenously the aliquot. I only have one comment: you assumed the density of glycerin to be the same as water (75g =75 mL), which is not the case. We usually do a weight:weight mixture. It's 94.5g of glycerin in 225g of water. It seems it worked for you well and 25% glycerin is not necessary, we have good results with 10% for bacteria and 20% for eukaryotic cells. cheers

[@buckeye0x0c]

I've been doing 50/50 glycerin and water, added to slurry to make about 12.5% glycerin. Am I totally wrong and it should be by weight?

[@joverstreet24]

So, are we looking for around 25% by weight or by volume?

[@billburns720]

The density of glycerin is 1.258 times that of water, so I'd guess that at 78 grams, it was actually 70 ml of glycerin?

[@billburns720]

@@joverstreet24 it would be 25% by volume. Water weighs 1g per 1 ml. 225 ml would be 225 grams. You can see Martin weighing it this way. The issue is that Pure 100% glycerin is 1.258 times the density of water, so 75 ml of glycerin is 94.35 grams. If you're weighing it, you need to weigh out 94.35 grams which is still 75 ml of glycerin.

[@JBernhard72]

5:40 I just heat the mixture in a pot and let it simmer for a while. let cool then pour into sanitized (Star San) mason jars for storage until needed. Been freezing yeast for years. And I use 50mL tubes.

[@nsmith1388]

Started doing this a couple years ago and it's great. Then I bought some yeast recently and decided I needed to go all in on freezing yeast... Almost $40 for two packs of yeast that I paid $25 for a couple years ago!! This saves so much money. Thanks for sharing!

[@jtc95]

Same! Liquid yeast is way too expensive (especially when getting it shipped insulated) but this makes it hurt a lot less. It’s pretty simple too, the first time I was intimidated but it’s pretty simple honestly

[@TheBruSho]

I can only imagine how many freezers you have in that house haha, great vid Martin

[@JollyLizardBrewing]

Would have loved to have seen you bring on a biologist/chemist and perform yeast cell counts on the vials and starter you made to back up the procedure. Maybe a good follow up video!!!!

[@AlbeeSoaring]

I was thinking the same thing.

[@ClausLucking]

I did a cell count last week on a 1 liter starter from a 50 ml. frozen yeast and counted 100 billion cells. If anyone can use it for anything. Now running a starter on this one liter to get approx. 590 billion cells for a brew on Sunday. Will count again on Saturday to check.

[@AlbeeSoaring]

@@ClausLucking How do you do a count? Do you send out to a lab for examination?

[@JollyLizardBrewing]

@@AlbeeSoaring kzbin.info/www/bejne/hpm1iZV5gNlknrs One of many

[@vikramjitsingh4538]

you can check out the process of counting yeast cells online.......there are many websites.......you require a microscope with a minimum 400x magnification, some plastic tubes, a haemocytometer and a staining dye like methlyne violet or blue, and follow the steps.........there's also a video on KZbin by white labs........have fun....cheers

[@NaibewKontumbia]

Thank you so much bro for your nice trick.

[@preuc3367]

Thanks for the video

[@AlbeeSoaring]

Great information. Ive been learning how to harvest yeast and save it for other batches so this is my next natural step. Harvesting the yeast has been fun and rewarding especially when I have been able to make 3 beers from just 1 single pack of yeast.

[@JosVanTongeren]

Thanks for Sharing! I look forward to the tips and tricks I will find in the comment section of this video. If there are any pro brewers watching or pro yeast company's watching I am curious if they have any improvement points of this method. Maybe a BruLab episode with for example Dr. Laura Burns on this topic? Keep up the good work Brulosophy team!

[@MadMax00215]

I'm still doing the fridge thing, and only recently I had a US-05 that I saved that wouldn't do anything in a starter. Poor thing died in the fridge after only 6 or 7 months. RIP US-05 slurry, RIP mate! Luckily I had a dry packet that I used on brew day. I'd love to have a pressure canner for lots of things. Great video!

[@pdescham496]

Awesome stuff... I guess I'll need to find your video on how to tell how many cells are in your cultured stater and make the final slurry.

[@ClausLucking]

I'm using more or less same procedure. Except that I mix water and glycerin just before use without the pressure canning. And it has worked fine for years.

[@Cleanshave50]

How long have you been able to successfully store the yeast for without the pressure canning?

[@ClausLucking]

@@Cleanshave50several years. And I will not start doing it. Just make sure everything is sanitized.

[@Cleanshave50]

@@ClausLucking great advice. Thank you!

[@chrisfranks5871]

What is the purpose of the pressure canning? Is it for sanitation/ preservation, or does it alter the glycerin in some way?

[@joverstreet24]

@@chrisfranks5871my question also.

[@alexavery3580]

Awesome video Martin! Thank you for sharing! One question- what are your thoughts on going straight to a 1L starter versus a smaller initial step up? I ask because Chris and Jamil's yeast book recommends a maximum factor of 10x for each step.

[@thombaz]

I am not the best in Physics, but I think that alcohol bath just makes it freeze faster, as It's colder then freezed water, but can take away heat faster then just cold air. (?)

[@polarbaits4733]

Congratulations on the video! One question: when you thaw the yeast and make a starter, how do you estimate the quantity of starter and yeast needed to ferment a batch?

[@jeffroach3722]

Bad ass 🔥

[@elibadran956]

Liquid vs dry vs Harvested! Thanks for the great informative videos. I'm certainly enjoying the show and learning. It would be great (please!) if you can do a single mash for same yeast strain in different form liquid vs dry and resolve the infamous debate, is the final beer really different? (Saisons and some unique taste profile beers dominate this debate) Also, any notable change of beer taste overtime with harvested yeast?

[@Caprifool]

If you're under 1000 feet the canning pressure is 10psi. 15 is to compensate the lower atmospherical pressure above 1000 feet. 👍🏻

[@sergioyap3196]

Do you have to pressure can the cryopreservative? Could one sterlize the preservative by heating the solution in a mason jar in a pot of boiling water? Don't really want a pressure canner.

[@Dayman.]

What is the purpose of pressure cooking the cryopreservative? Is it just to steralize the solution? I've btw been doing this for about 2 years now and never used a pressure cooker, just sanitize everything. No issues so far.

[@andyh7537]

@Dayman - Yes. The pressure cooker completely sterilizes the cryopreservative.

[@SyBernot]

I'm pretty sure the pressure canner is not "required" to make the solution, but to sterilize it. You could do this stove top by boiling water then adding in the glycerin and pouring directly into a preheated and sterilized mason jar and be pretty confident that you have a sterile solution.

[@schwop]

You might also try filling boiling water into a keg and put 15PSI of pressure on it

[@SyBernot]

@@schwop The point of the pressure in a pressure cooker is it raises the boiling point of the water allowing you to bring the temp above 100C. Putting water into a vessel and adding pressure will not raise the temp above 100C

[@eachday5705]

You need 120°C.

[@herbstava]

It’s just a small version of an autoclave. The pressure just allows water to boil at a higher temperature ensuring sterilization. Another method is to pass the solution through 0.2 micron filters… but those are hard to come by

[@nateuerdaz8038]

I wonder if I could use an instant pot instead of a pressure canner....

[@zainmallett]

I can’t get my hands on isopropanol. Would an ethanol bath be fine?

[@fdk7014]

What does the pressure cooking do? Is it just for sterilization?

[@bradmcmahon3156]

I just mix the glycerine/water mixture in a 500 mL Schott borosilicate flask and microwave that for a few minutes. That's sanitary enough for me, particularly when you are doing the other steps outside of a sterile environment.

[@NoMusiciansInMusicAnymore]

Interesting video but I'd love some more details, what does the canner actually do that, say, adding boiling water wouldn't do? what does the defrosting regiment look like? I am assuming you wouldn't just drop a vial in an erlenmeyer flask and turn the stirrer on

[@jean-raphaellavoie34]

Hi Matin, I was super excited to reuse the yeast I frooze following this method but 24 hours after sitting on a stir plate gravity has not changed a bit. I'm starting to wonder if I did not mix the yeast and the glycerin mixture enough? Any idea on what might have gone wrong here? I belive the yeast I frooze was from a fresh starter.

[@f.lapointe4343]

Lallemand will stopped to produce its LalBrew Kôln yeast... so time to do some freezing 😊

[@philipdrew1066]

Would a domestic pressure cooker do instead of buying a canning pressure cooker?

[@brewpilot8958]

I might have missed it, how many total yeast cells did you get from the 20 billion vial in 1 liter starter?

[@CascadesHomebrew]

Well made video. Would you normally pitch that slurry from your 1L starter into a batch (say 5.5 gals of a 1.055 ale) or should that be built up a second time?

[@vikramjitsingh4538]

it's a bit difficult to tell without actually doing a cell count, however a step up would be a good idea........cause under pitching would have off flavors in the beer.......cheers

[@CascadesHomebrew]

@@vikramjitsingh4538 That seems like a good plan. One yeast calculator predicts about 150B cells from a 1L starter, but there is not much difference between starting with 5B cells or 20B cells. A 1.5L starter gets over 200B, but it might be better to start smaller (say 300ml) then step that up.

[@vikramjitsingh4538]

@@CascadesHomebrew try brewers friend for step up calculations.........also use a stir plate......u would get substantial growth and use very little, just a dust of zinc sulphate.......ur yeast will thank you for it.......cheers

[@giantbeat1]

Yeah I thought somehow the glycerin & water needed the pressure to combine. I'm gonna just boil it- Thanks comments!

[@JasonSmith-nt6rl]

Can this work with mixed cultures yeast/bacteria?

[@bobbob-ze9zo]

like # 156- great job!!!

[@user-dx4dl5bn8p]

Not gonna lie, I was pretty excited for this until I saw you doing it. I think I'll keep buying dried packets.

[@MooreDamian]

Great video Martin but not sure your "20 billion cells" in each of your frozen vials is correct? The yeast package shown in your video states 200 Billion Cells in 155ml. That's 1.29 billion cells per ml. So correct me if I am wrong on the following (& it would be great to be wrong with this) but each of your vials has a maximum amount of c. 7.75 billion cells - assuming the yeast is 100% viable when you are using it? However, according to the Brewer's Friend calculator, a 1.4L starter will get you just over the (Ale) threshold to pitch, so your vials are still good to be used on that basis. Then we have lager yeast which needs even larger pitching rates - thank God for dried yeast like W-34/70! TBH this area is probably the biggest source of confusion for me over the years, which is why I have only harvested yeast infrequently & very unscientifically. As per what someone below has already mentioned, to be 100% confident with the cell count, you'd need a microscope etc to go (viable) cell counting. Thanks again for the video.

[@btlarsen]

If you use the right kveik, you can just drie it and freeze it

[@LeJimster]

I wonder how many years these yeast will be viable for.

[@thibw638]

Great video! Although I’m not getting why the pressure is needed.. what’s the purpose?

[@orange-micro-fiber9740]

Same question.

[@thombaz]

For something to be sterile you need to reach 121C, and keep it at that temperature for half an hour (but that depends on how much stuff you sterilize). You need 15PSI to reach that temperature (as water becaome gas at around 100C under normal pressure conditions). Under 121C you can not sterilize as there are some stuff that can survive lower temperatures.

[@orange-micro-fiber9740]

@@thombaz why do you need to sterilize if you freeze it.

[@thombaz]

@@orange-micro-fiber9740 Freezing do not makes It sterile. It puts stuffs into dormant state, but as you start your yeast culture, you very likely start to grow your contaminations too, which is not a great idea if you start from small and grow out a big culture from it (as the nasty stuff will grow big with it). So contamination at this small sizes is a big problem, as It's going to grow big in your starter/beer.

[@sandhill9313]

For years I've just bought a couple of ounces of IDY and keep it in a jar in the freezer. It seems to last forever with no effort whatsoever.

[@murraywigzell9431]

What is the purpose for the pressure cooker? If the mason jar is sealed then the pressure inside the jar does not change. Is it to allow a higher boil point?

[@TheBrulosophyShow]

Yes exactly.

[@pskahan]

The temperature of steam at 15 psig is 250F. Wouldn't putting the jar of cryopreservative in a 250F oven for the same length of time achieve the same goal?

[@RedHotBagel]

Does water get hotter than 212°F if you boil it harder? Spoiler alert, not if it is not under pressure. You want these higher temperatures to make sure spores and such don't survive the process. But in a 250°F oven, water, as long as it is still fluid, doesn't ever reach 250°F.

[@justthebrttrk]

Water cannot exist at sea level pressure in liquid form above 212 degrees because at that point it turns into a gas. There would be no liquid left and it would never get to 250 degrees.

[@pskahan]

If the container is sealed and can hold the 15psig the solution will generate at 250F, the solution will reach the temperature of the oven. Both of the above statements assume the water can escape the container.

[@RedHotBagel]

@@pskahan the steam usually can, because you don't want to build bombs...

[@zkosslow]

Thermodynamics is a bitch.

[@danchuey]

Tap water for everything?

[@RedHotBagel]

You probably want to use RO or distilled, depending on your local water composition and treatment.

[@JBernhard72]

boiled tap water that has been cooled works for me

[@freehlr]

I care less about whether I can simply revive a strain in a flask after three years of frozen storage and more about the quality of beer such yeast subsequently produces. Any sensory impressions/comparisons on how the beer turns out using three-year-old frozen/thawed yeast? On another note, this whole process seems like a PITA. I'd rather pay for a fresh pitch, and I haven't come across a strain that is so unique and hard to find that it warrants the PITA process of freezing it. That said, great video, as usual :-)

[@NoMusiciansInMusicAnymore]

Might as well just buy the beer as there's never really any brands or flavours that are so unique and hard to find that it warrants the PITA process of brewing it.

[@eriksimoes80]

I propagated a 3 year old yeast, however, it was stored in slants (not frozen). During the starter I could see that the color was brown, not milky as expected. I used it in a English Porter and the result was terrible. It was a diacetyl bomb. Notably the yeast was of low quality.

[@riskyb250]

I don't understand the liquid yeast obsession. Dry yeast works great these days and there are plenty of strains available. They keep for years as long as they are sealed in a refrigerator. I would only ever use liquid as a last resort While this is a cool process and I'm glad I got to watch the video on it. This is not something I want to bother doing. Buying all this equipment just isn't worth it